Lichen colonization and associated biodeterioration processes on ancient bricks of the Gonbad-e Qābus tower, UNESCO World Heritage Site, Iran

Knowledge of the influence of architecture-related microclimatic on the diversity and distribution of lichens causing biodeterioration on brick substrate surfaces in Iran has received less attention. One of the most prominent works of Iranian architecture is the brick tower of Gonbad-e Qābus in the ancient city of Gorgan (Jorjan), which shows widespread lichen colonization. In addition to the aesthetic aspect, these lichens destroy tower bricks. In this study, lichen communities on its outer walls were characterized in terms of diversity and distribution for architectural (wall geometries) and microclimatic (wall orientation) features, and their relationships with substrate biodeterioration were evaluated. The results show that the colonization and distribution of lichens in different parts of the building are different according to the geometrical shape, wind and rain direction, and the sunlight angle. Also, lichens are responsible for the biodeterioration of brick surface layers through the penetration of hyphae into the pores and porosities, the secretion of acids, and the chemical modification of some mineral constituents. Knowledge and investigating the effects of architecture-related microclimatic on the distribution and diversity of biodeterioration factors can help in the preventive conservation of cultural heritage.